This invention relates to a finish dirt scraper with an improved damping device in the nature of a coil compression spring and hydraulic system working in combination.
Finish scrapers to be used in land leveling operations are known in the art. U.S. Pat. Nos. 4,704,812; 3,889,404; 4,490,929; and 4,307,522 are noted in the disclosure in my U.S. Pat. No. 5,794,714 and in the disclosure in my U.S. Pat. No. 5,307,570 which are hereby incorporated in and made a part of the disclosure in this specification. This invention is an improvement over the commercial inventions disclosed and claimed in my U.S. Pat. Nos. 5,794,714 and 5,307,570.
None of the known references or any other known device is adapted to ground leveling wherein uneven terrain is partially leveled and large clumps of dirt are broken up in advance of a leveling blade and bucket in the rapid manner accomplished by using the invention described herein in greater detail.
As disclosed in my U.S. Pat. No. 5,794,714, the use of finish dirt scrapers has become an ever increasing important piece of equipment in quickly leveling ground for construction purposes. Although the commercial invention disclosed and claimed in my U.S. Pat. No. 5,794,714 was a tremendous improvement in equipment useful for quickly leveling dirt which may be contaminated with rocks and other debris, moving the finish dirt scraper rapidly results in an enhanced problem known as xe2x80x9cbouncexe2x80x9d. The term bounce includes tendency of the cutting edge of the bucket to dig too deep or too shallow when collecting and removing a slice of dirt from the area being worked. Bounce also includes the concept of excessive vibration of the bucket during filling and transportation. Also, bounce may occur when one portion of the bucket cutting edge reaches the material being collected slightly ahead of the other edge portion of the bucket producing a horizontal bouncing effect from the bucket jumping back and forth form one side to the other in a somewhat uncontrollable manner. This has been a problem in other types of heavy equipment used to move dirt and my U.S. Pat. No. 5,307,570 discloses and claims a damping device useful in connection with controlling the bounce during the loading and transportation of large buckets of dirt and other frangible products. The damping device disclosed and claimed in my U.S. Pat. No. 5,307,570 does not function as effectively in controlling bounce in finish dirt scrapers such as disclosed and claimed in my U.S. Pat. No. 5,794,714. The damping device disclosed in my U.S. Pat. No. 5,307,570 works well for scrapers which actually load the dirt and debris, where the weight of the dirt and debris in the bucket helps control the bounce, after the initial contact of the material has been stabilized. Utilizing a finish dirt scraper, the scraper begins to load smoothly but when the force of weight from the scraper is rejected from the opposing force of the dirt, e.g. clay soil, it creates an uncontrollable bounce of the entire scraper, over time causing structural damage to the scraper, and severely hampering production of the finished dirt work.
This invention is a hydraulically controlled shock absorber system which includes a compression-expansion spring and hydraulic system working in combination.
This invention includes a compression-expansion coil spring which encircles a shaft with a piston mounted on the upper end of the shaft adapted to move up and down in a cylinder which works in a hydraulic oil. The upper end of the cylinder in which the piston operates contains a constricted orifice. In an upper projection of the sleeve, there is an additional oil reserve chamber. Thus, when the piston is moved upward forcing oil through the restricted orifice, it is partially retained in the oil reserve chamber. This creates a typically hydraulic resistance as the piston is forced upward.
In order to maintain a degree of equilibrium in the system, this invention includes an oil return line which has an upper opening in the upper oil reserve chamber and a lower opening into the lower chamber in which the piston works. Thus, oil may free flow by gravity and from compression from the upper oil reserve chamber into the chamber below the piston as the piston moves upward. Also as the piston moves upward a partial vacuum is produced below the piston in the cylinder which helps pull oil through the oil by-pass line into the space in the lower chamber of the cylinder vacated as the piston is forced upward.
When a bump in the soil is passed and the piston returns downward to its normal position, oil flows upward through the bypass oil line into the upper oil chamber and some will pass back through the orifice into the lower oil chamber in the cylinder above the piston. Thus, the system operates on a continuous basis to dampen bounce in the bucket.
The bottom of the shaft is hingedly attached to a dirt shoe which operates up and down as the finished dirt scraper traverses uneven ground. The principle function of the coil spring is to always maintain the dirt shoe on the ground and to avoid bouncing of the dirt shoe which could distort the damping effect of this invention. The dirt skid shoe has replaceable wear plates attached thereto. Each skid shoe is hingedly mounted on the bucket by means of a front hinge. The skid shoe is held in working relationship with the damping device by means of a pin and key arrangement so that it may be easily and quickly removed and replaced as it becomes worn and inoperable, or replace parts.
A breather tube projects outward from the upper portion of the upper oil reserve chamber in order to relieve any entrapped air, but which is adapted to prevent the loss of oil from the system.
The upper end of the damping device of this invention is hingedly attached to a projection extending approximately perpendicular from the rear wall of the scraper. The attachment may be by pin and key connection. The projection may be welded, bolted, or otherwise attached to the rear of the bucket and may contain a series of openings to provide additional adjustments. The skid shoe is hingedly attached to the lower portion of the bucket by means of a xe2x80x9cUxe2x80x9d shaped mounting bracket attached to the bottom area of the bucket and hingedly attached to the shoe.
When the shoe of the damping device of this invention makes contact with the soil, the shaft is pushed upward which causes the piston to move upward while at the same time the coil spring is compressed, thus keeping the skid shoe on the ground, which may be uneven. The flow of oil through the restricted orifice creates a predetermined flow rate inside the cylinder. This allows the bucket of the scraper to move up and down at a controlled rate to provide a more harmonious contact between the opposing forces which create bounce. The coil spring around the exposed cylinder shaft forces the skid shoe to remain on the ground.
When the shoe of the damper makes contact with the soil, the cylinder contracts slowly from the weight of the scraper, the flow of oil is restricted, with a predetermined flow rate inside the cylinder allowing the scraper to lower at a controlled rate, therefore having a more harmonious contact with the opposing force. Should the ground force exceed the weight, the process is quickly repeated because the shoe remains on the ground kept there by the coil spring around the exposed cylinder shaft uninhibited by the flow restrictor because it is free flowing in the opposite direction.
Generally, at least two damping devices of this invention are included on each finished dirt scraper. More than two may be used in particularly severe conditions and only one may be used with a particularly small finish dirt scraper.